Modernly, manufacturers of power tools desire to reduce the cost of producing power tools by providing designs that provide the product with a high level of robustness while reducing complexity at the assembly level and minimizing components that do not add value to the product. Manufacturers are further challenged by the demand of modern consumers for tools that are relatively smaller in size, lighter in weight and more powerful.
Accordingly, it is highly desirable to eliminate threaded fasteners from the power tool, such as those that are typically employed to couple the transmission assembly to the clutch mechanism. The use of threaded fasteners in these situations necessitates the incorporation of bosses to the transmission assembly and the clutch mechanism that tend to enlarge the size of the tool and which add a degree of weight to the power tool. The fastening process itself tends to be relatively slow and errors in the process, such as over tightening, which can lead to the stripping of threads or cracking of the components, or under tightening, which can create an interference that prevents the components from operating properly, are possible. The use of torque controlled fastening equipment is known to alleviate such processing errors, but this equipment can be relatively expensive to purchase and operate.
It is also desirable to better integrate the clutch mechanism with the transmission assembly. Many of the known power tool designs employ a modular design that is based on a power tool having no torque controlled clutch. In cases where precise torque control was needed, a clutch module could be coupled to the output end of the base tool. While configuration in this manner effectively accommodated consumer demands for both the base and torque controlled models in an economical manner, the modular configuration tended to add considerable length and weight to the power tool.